The latest group, who told police they are Iranian, included both adults and children, French officials said.

"Overnight towards 4am , what appears to be an inflatable boat carrying nine people crossed over to England after apparently leaving from Calais" in northern France, maritime authorities told AFP.

A French helicopter was dispatched but the vessel was finally intercepted near Dover by British authorities, they added.

On Tuesday, a group of 17 Iranians - 14 men and three minors - managed to reach Dover after stealing a fishing trawler from the French port of Boulogne-sur-Mer and hotwiring it.

Ingrid Parrot, spokeswoman for maritime authorities in northern France, called the crossing “unprecedented” as the boat was much bigger than the usual smaller craft used.

British officials said the Iranians' asylum cases would be reviewed.

Thousands of migrants from Africa, the Middle East and Asia attempt to sneak into Britain by stowing away on trucks crossing to England.

Far fewer try do so by crossing in boats, though the numbers have been rising.

According to French authorities, the number of operations to either arrest or save migrants attempting to cross the Channel from France has almost doubled in 2018 compared to last year to 23 - up from 12 last year.

France shut the notorious “Jungle” migrant camp in Calais late 2016 and both French and UK authorities said that this would put stop to attempts to illegal enter Britain.

But police say the problem has been displaced along the coast. Last month, they evicted 1,800 from the Grande-Synthe camp outside Dunkirk in the fifth such operation in five months.